Methods and means for rolling metal powder



March 21, 1967 E. GEHRING g gm 'ygg METHODS AND MEANS FOR ROLLING METAL POWDER Filed April 27, 1964 United States Patent METHODS AND MEANS FOR ROLLING METAL POWDER Eckard Gehring, Dusseldorf, Germany, assignor to Schloemann Aktiengesellschaft, Dusseldorf, Germany Filed Apr. 27, 1964, Ser. No. 362,864 Claims priority, application Germany, May 3, 1963, Sch 33,230 1 Claim. (Cl. 18-9) In the rolling of metal particles, such as metal powder or metal, granules, into strips or the like, the rolling speed, that is to say, the peripheral speed of the rolls, which is also the speed at which the rolled prodpct leaves the rolls, does not admit of being arbitrarily increased. This is to be attributed to the fact, amongst others, that the stock located within the gripping range of the rolls has to be accelerated up to the rolling speed by frictional forces in order to overcome its inertia. By the gripping range of the rolls is meant the space between the roll peripheries within which the rolls exert compression upon the particles. This compression ceases at the plane containing the axes of the rolls, after starting at a plane parallel thereto, the position of which is determined by the angle of friction between the roll peripheries and the particles. The gripping angle is the angle subtended at the axis of each roll by the part of the roll periphery bounded by the two abovementioned planes. These frictional forces form a pre-requisite for the rolls, and stand in a functional relationship with the inertia forces of the metal particles. The greater the peripheral speed of the rolls, and therefore the greater the rolling speed, the greater must also be the accelerating forces acting upon the stock, in order to bring the stationary stock up to the final speed, that is, the rolling speed. With pairs of rolls the axes of which lie in a horizontal plane, there act upon the stock, as accelerating forces, not only the acceleration due to gravity, but also the friction between the roll surfaces and the stock. The acceleration of the stock caused by the friction is limited by the accelerating distance, which is fixed by the gripping angle of the rolls, and which, with the same gripping angle, can only be lengthened by increasing the diameter of the rolls. On technical grounds, however, as well as on ground of economy, one is constrained to keep the dimensions of the rolls, as regards their periphery or diameter, as small as possible. The limitation associated therewith in the accelerating distance for the stock constitutes at the same time a measure for the maximum rolling speed. At the same time, however, the rolling speed is also dependent upon the width of the roll gap. The wider the selected roll gap, the greater must also be the rolling range in which the deformation of the metal particles or granules, for the same compaction or consolidation, takes place. The increase of the deformation range or gripping range of the rolls causes however at the same time a further shortening of the accelerating distances for the metal-granules, and, in dependence thereon, a reduction in the rolling speed.

The object of the invention is to enable an increase in the speed of rolling to be obtained with 'a constant roll diameter and roll gap. According to the invention this is attained by positively imparting to the metal powder or metal granules, from outside such a kinetic energy that their final speed in the gripping range of the rolls corresponds approximately to the rolling speed, the metal powder or granules being supplied in such quantities that their kinetic energy remains operative during the rolling operation. Owing to this approximately equality in speed between the stock supplied and the speed of rolling, the rolls do not need to accelerate additionally the stock supplied, so that the factor based thereon with respect to the 3,399,735 Patented Mar. 21, 1967 ice upper limitation of the. rolling speed ceases to apply. Hence, as compared with the conventional method, in which the stock acted upon the roll merely by its own weight, the rolling speed can be materially increased. For the effective maintenance of the kinetic energy of the stock during the rolling operation, the quantity supplied is advantageously selected so great that the space enclosed by the gripping angles of the pair of rolls remains filled without any heaping or slope.

In a further development of the invention the speed of supply of the stock in the roll gap is kept greater than the rolling speed. The stock thereby exerts, owing to its braking, in the region of the gripping angle of the rolls, a pressure upon the stock already located between the rolls. This raising of the pressure on the entry side of the rolls results in an increase of the gripping angle, so that for the same roll diameter, strips of greater thickness can be rolled. The apparatus for feeding the stock to the rolls with the required quantity and speed consists advantageously of a conveyor belt, charged from a receiving hopper and running at a variable speed, which, in the case of rolls arranged horizontally side by side, supplies the stock to the roll gap, after falling through a definite height according to thespeed of feed required. In the case of rolls arranged vertically, that is one above the other, the stock is conveniently supplied by the conveyor belt to a centrifugal device provided with blades, which fiings the stock into the gripping region of the rolls. Rolls arranged horizontally side by side may also be preceded by such a centrifugal device.

Apparatus for feeding stock to be rolled into the gripping range of the rolls by the method according to the invention is illustrated by way of example in the accompanying drawings, in which:

FIGURE 1 shows the arrangement of the feeding device with rolls arranged side by side in a horizontal plane; and

FIGURE 2 shows the feeding device with rolls arranged one above another in a vertical plane.

According to FIGURE 1, the stock 4 is supplied to the rolls 1, by way of a conveyor belt 2, from a receiving hopper 3. The stock to be rolled, in the form of granules or metallic powder, is supplied to the conveyor belt in accurately dosed quantities, and falls, after leaving the conveyor belt 2, into the gripping range 5 of the rolls 1, which are arranged with their axes in a horizontal plane. The height of the conveyor belt 2 above the rolls 1 is such that the metal powder, after falling freely through the height b, has acquired the same or approximately the same speed as the peripheral velocity or rolling speed of the rolls. The speed of motion of the conveyer belt 2 can be varied, so that the quantity of stock can be accurately dosed. The quantity of stock supplied should not accumulate in the gripping range of the rolls, in order that the acceleration energy of the stock may remain fully operative within the gripping range of the rolls. The quantity of stock supplied is therefore adapted to the absorption capacity of the rolls.

The apparatus illustrated in FIGURE 2 for carrying out the method likewise comprises the receiving hopper 3 and the conveyor belt 2, with the addition of a centrifug'al device 6. The rolls 1 however are here arranged one below the other with their axes in a vertical plane. Here the energy of acceleration of the stock 4 is provided by the centrifugal device 6, which supplies the metal powder to the roll gap or gripping range of the rolls in a horizontal direction, by centrifugal action. The speed of revolution of the centrifugal device is variable, in order to enable the acceleration prescribed by the power of absorption of the rolls to be positively imparted to the stock.

I claim:

Apparatus for rolling discrete metal particles, such as metal powder and metal granules into strips comprising a conveyer belt, a hopper for feeding metal particles to said belt, said hopper being located above said belt and having an outlet close to the belt, a pair of reducing rolls located in vertically spaced relationship with their axes horizontal and in vertical alignment, said rolls being located so that the space between the rolls is laterally spaced from but below the discharge end of said conveyer belt, and a bladed centrifugal device positioned below the discharge end of said conveyer belt and in advance of said rolls as regards the direction of rolling whereby metal particles falling by gravity from the discharge end of the conveyer References Cited by the Examiner UNITED STATES PATENTS 2,341,732 2/1944 Marvin 264--11 2,904,829 9/1959 Heck 264-411 3,095,262 6/1963 Maish et a1 264-111 ROBERT F. WHITE, Primary Examiner.

belt drop onto the centrifugal device and are hurled t0- 15 F. S. WHISENHUNT, I. R. HALL, Assistant Examiners. 

